Vibrational characterization of the pesticide molecule Tebuconazole

Abstract

Pesticide use worldwide exhibits a positive effect on agricultural production while it may negatively affect organisms living in soil, water or the air. Importantly, numerous negative health effects also occur in humans exposed to (accumulated) pesticides or their metabolites over a long period of time. To prevent both environmental catastrophes and adverse human health impacts, initial studies of the selected pesticides need to be performed together with the constant post-approval control; risk assessment analysis and on site monitoring have to be continuously carried out. Given this, Raman spectroscopy, especially surface-enhanced Raman spectroscopy (SERS), during the last decade has become a powerful analytical technique since it can offer quick, selective, and in situ detection of selected pollutants found in analyzed samples at very low concentrations. Moreover, the structural changes caused by the pollutant-biomacromolecule interaction can also be recognized in the molecule-specific Raman spectral signatures of biomolecules. In this study, we report a vibrational characterization of the fungicide molecule Tebuconazole (TB) which is listed to be a possible carcinogen. Even though its international and common use there is no evidence about the use of Raman/SERS spectroscopy to detect it sensitively and selectively as well as to analyse its impacts on biological systems. Therefore, we have recorded and calculated Raman and infrared spectra of TB. Furthermore, SERS spectra of TB were also registered and comprehensively analysed in view of the employed SERS substrates, dependence on the excitation wavelengths and pH of the analysed molecular systems. The molecule of TB interacts preferentially through the triazole moiety with the colloidal metal nanoparticles (NPs) whereas the silver NPs prepared by reduction of silver nitrate with hydroxylamine hydrochloride resulted to be the most effective ones. Consequently, the limit of detection was determined to be 1.4 μM≈430 ppb. The present paper thus could serve significantly for further investigations focused on both conducting vibrational analyses of structurally related molecules as well as providing a more precise explanation of the mechanism of action of TB and its influence on biological macromolecules.

Keywords: Density functional theory (DFT); Limit of detection (LOD); Pesticide (fungicide); Surface-enhanced Raman; Tebuconazole; Vibrational spectra.